This invention relates to molded case circuit breakers operable in response to fault currents to open the contacts and interrupt a circuit in which the circuit breaker is connected. While not limited thereto this invention relates to circuit breakers of the aforementioned type which are operable upon high fault currents to limit the peak let-through current. The circuit breaker of this invention is intended to handle moderately high fault current levels which upon interruption can cause explosive forces and expel hot ionized arc gasses. Circuit breakers of this type are known and have generally been useful for their intended purposes. However, this invention relates to improvements thereover.